ber

README

BER Package

This package is a fork of the standard library encoding/asn1 package, adding Basic Encoding Rules support for use with github.com/k-sone/snmpgo.

Golang Compatibility

This package aims to maintain compatibility with earlier versions of Golang as best as possible. Travis CI builds ensure the below compatibility.

Version	Compatibility
1.0.0	Go 1.5 - 1.8
1.1.x	Go 1.8 - 1.14

License

Copyright (c) 2009 The Go Authors. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

   * Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.
   * Neither the name of Google Inc. nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Documentation

Overview

Package asn1 implements parsing of DER-encoded ASN.1 data structures, as defined in ITU-T Rec X.690.

See also “A Layman's Guide to a Subset of ASN.1, BER, and DER,” http://luca.ntop.org/Teaching/Appunti/asn1.html.

Index

• func Marshal(val interface{}) ([]byte, error)
• func Unmarshal(b []byte, val interface{}) (rest []byte, err error)
• func UnmarshalWithParams(b []byte, val interface{}, params string) (rest []byte, err error)

Functions

func Marshal

func Marshal(val interface{}) ([]byte, error)

Marshal wraps the asn1.Marshal function

func Unmarshal

func Unmarshal(b []byte, val interface{}) (rest []byte, err error)

Unmarshal parses the BER-encoded ASN.1 data structure b and uses the reflect package to fill in an arbitrary value pointed at by val. Because Unmarshal uses the reflect package, the structs being written to must use upper case field names.

An ASN.1 INTEGER can be written to an int, int32, int64, or *big.Int (from the math/big package). If the encoded value does not fit in the Go type, Unmarshal returns a parse error.

An ASN.1 BIT STRING can be written to a BitString.

An ASN.1 OCTET STRING can be written to a []byte.

An ASN.1 OBJECT IDENTIFIER can be written to an ObjectIdentifier.

An ASN.1 ENUMERATED can be written to an Enumerated.

An ASN.1 UTCTIME or GENERALIZEDTIME can be written to a time.Time.

An ASN.1 PrintableString, IA5String, or NumericString can be written to a string.

Any of the above ASN.1 values can be written to an interface{}. The value stored in the interface has the corresponding Go type. For integers, that type is int64.

An ASN.1 SEQUENCE OF x or SET OF x can be written to a slice if an x can be written to the slice's element type.

An ASN.1 SEQUENCE or SET can be written to a struct if each of the elements in the sequence can be written to the corresponding element in the struct.

The following tags on struct fields have special meaning to Unmarshal:

application specifies that an APPLICATION tag is used
private     specifies that a PRIVATE tag is used
default:x   sets the default value for optional integer fields (only used if optional is also present)
explicit    specifies that an additional, explicit tag wraps the implicit one
optional    marks the field as ASN.1 OPTIONAL
set         causes a SET, rather than a SEQUENCE type to be expected
tag:x       specifies the ASN.1 tag number; implies ASN.1 CONTEXT SPECIFIC

If the type of the first field of a structure is RawContent then the raw ASN1 contents of the struct will be stored in it.

If the type name of a slice element ends with "SET" then it's treated as if the "set" tag was set on it. This can be used with nested slices where a struct tag cannot be given.

Other ASN.1 types are not supported; if it encounters them, Unmarshal returns a parse error.

func UnmarshalWithParams

func UnmarshalWithParams(b []byte, val interface{}, params string) (rest []byte, err error)

UnmarshalWithParams allows field parameters to be specified for the top-level element. The form of the params is the same as the field tags.